Carbon steel A105 Flanges 6", Technics : Forged way

The slip-on flange has a low hub because the pipe slips into the flange prior to welding. It is welded both inside and out to provide sufficient strength and prevent leakage. Slip-on flanges are all bored slightly larger that the o.d. Of the matching pipe. They are preferred over welding neck flanges by many users due to their lower initial cost, but final installation cost is probably not much less than that of the welding neck flange because of the additional welding involved.
Lap joint flanges:
the lap joint flange is practically identical to a slip-on flange except it has a radius at the intersection of the bore and flange race. This radius is necessary to have the flange accommodate a lap joint stub end. Normally, a lap joint flange and a lap joint stub end are mated together in an assembly system.
Blind flanges:
the blind flange is a flange without a bore. It is used to close off the ends of a piping system andor a pressure vessel opening. It also permits easy access to the interior of a line or vessel once it has been sealed and must be reopened.
Socket welding flanges:
the socket welding flange is similar to a slip-on flange except it has a bore and a counter bore dimension. The counter bore is slightly lager than the o.d. Of the matching pipe, allowing the pipe to be inserted into the flange similar to a slip-on flange. The diameter of the smaller bore is the same as the i.d. Of the matching pipe. A restriction is built into the bottom of the bore which sets as a shoulder for the pipe to rest on. This eliminates any restriction in flow when using a socket welding flange.